The invention pertains to the field of lawnmowers. More particularly, the invention pertains to lawnmowers of the riding type having rear wheel independent suspension.
The present invention is described with respect to its use on riding lawn mowers, particularly self-propelled machines fitted with rotating blades for cutting turf grasses. In the most favored typical design, the rider sits atop a three or four wheeled machine, while one or more blades rotate about a vertical axis within a mower deck mounted at the underside of the machine, to cut grasses as the machine moves across the surface being mowed.
In many typical riding mowers, the cutter deck is configured as either a ground-following deck or a floating deck. A ground-following deck typically rides on either two or four caster wheels and follows the contours of the ground. A floating deck is hung between the front and rear wheels and beneath the chassis by chains, links or other devices, being adapted to rise up when skids, wheels, rollers and the like attached to the underside of the deck make contact the lawn surface. Generally, the intent for such deck suspension system is to avoid continuing contact with the earth surface. The distance of the cutter deck from the earth surface is determined by the elevation of the chassis. When the mower crosses an earth-surface rise which is relatively severe, that is, short in horizontal length compared to the wheel base of the mower and great in height compared to the pre-set elevation of the mower deck, the deck frequently makes contact with the earth surface. Then, it is intended that the deck rises or xe2x80x9cfloatsxe2x80x9d upwardly, so the rotary blades do not hit the earth surface. Such designs work well for many kinds of unevenness, but scalping for certain earth surfaces and mower movements is still a problem. Even if there is no scalping, a variation of the height of the cutter deck relative to the earth surface is not wanted, as it varies the height of the cut grass.
Many typical prior art mowers have the wheels rigidly attached to the chassis. Thus, unevenness in the earth surface imparts a lot of up and down chassis motion. Some prior art mowers employ center-pivoting axles which somewhat reduce the vertical motion of the chassis when one wheel encounters unevenness. The related applications describe a preferred transmission steerable mower which has rear drive wheels which are independently driven and spring suspended from the chassis, and which has free pivoting caster front wheels, mounted at the outer ends of a pivotable axle or subframe. The cutter deck is suspended between the front and rear wheels.
Mowers with improved spring suspension systems reduce the amount of chassis motion when one or both drive wheels of a mower encounter uneveness in the surface being mowed. Drive wheel traction is improved. However, depending on the particulars of any non-rigid suspension system, the chassis is enabled to roll relative to the earth surface, such as, for example, when the mower is sharply turning or when the mower is traversing a steep hillside. When a mower rolls, a floating cutter deck moves closer to the earth surface and there can be a tendency for scalping of the turf by the cutter deck. An improvement in one of the related applications connects the cutter deck with the rear wheels, thereby ensuring that the cutter deck moves relative to the wheels and ground instead of relative to the chassis of the mower.
A problem still exists with the independent suspension system of the related applications. For heavier weight riders or mower accessories, such as grass catchers, the spring used in the suspension system limits the suspension. Rider discomfort occurs when the spring bottoms out. In addition, the collapsed spring can create coil bind which drastically reduces the life of the spring. Merely substituting a stiffer spring for the existing spring causes a harder ride when the load is light. A suspension that works effectively with a wide range of weight variations is therefore needed.
Briefly stated, a lawn mower includes a front wheel suspension system as well as a rear wheel suspension system. A load compensation adjuster is employed as part of the rear wheel suspension system that compensates for riders having significantly differing weights, as well as for weight changes occurring during the mowing operation, such as from grass clippings accumulating in a grass catcher bag.
According to an embodiment of the present invention, a mower includes a main frame; first and second rear wheels; and first and second rear suspension systems connecting the first and second rear wheels, respectively, to the main frame, wherein the first and second rear suspension systems each include a load compensation adjuster.
According to an embodiment of the present invention, a mower includes a main frame; first and second rear wheels; first and second rear suspension systems connecting the first and second rear wheels, respectively, to the main frame; wherein each of the first and second rear suspension systems includes a motor mount effective for mounting a motor; first and second upper links; first and second lower links; the first upper link and the first lower link pivotably connected on one end to a first vertical strut, the first vertical strut connecting an upper frame member of said main frame to a lower frame member of the main frame; the first upper link and the first lower link pivotably connected on another end to the motor mount; the second upper link and the second lower link pivotably connected on one end to a second vertical strut, the second vertical strut connecting the upper frame member to the lower frame member; the second upper link and the second lower link pivotably connected on another end to the motor mount; a spring bracket on the upper frame member between the first and second vertical struts; a rear suspension spring connected between a second spring bracket and either the motor or the motor mount; and a load compensation adjuster connected inside the rear suspension spring.